Key Concepts: Subdivision, Allocation, and Substitution Subdivisionīefore allocation and substitution is applied, subdivision can come to place. The cut-off system model applies the same modelling choices as ecoinvent versions 1 and 2 and is therefore also recommended for experienced users looking for continuity with their previous work. This model is easier to understand for first-time users. For users new to the database, ecoinvent recommends using the cut-off system model when starting to work with ecoinvent version 3. Users should understand the assumptions of the system model they choose to ensure that it serves the goal and scope of their study. The choice of system model is a responsibility of the user. This factor is reflected in the resulting impact scores, which are otherwise quite similar. “Allocation, cut-off by classification” and “Allocation at the point of substitution” differ solely in the way they treat waste and recyclable materials. All system models start from the same pool of individual processes of human activities (Undefined Unit Processes ( UPR)) and apply different assumptions to determine the supply (linking) and the distribution of impacts between producers and consumers of products and services (allocation and substitution).ĭifferent system models, namely, “Allocation, cut-off by classification”, “Allocation, cut-off, EN15804”, “Allocation at the point of substitution” and “Substitution, consequential, long-term”, are offered to meet the demand of different types of studies. System models set the methodological rules to calculate the database.